My copy is lovely sharp at every focal length. In my opinion its an awesome lens, very wide, the only wide option for 1,6 crop factor SLR's. Works awesome on my 350d. Zoom/focuses very smooth and quickly, and its lightweight.
I do many landscape and architecture shots and this lens is just perfect for that. I love the width of the images that I now shoot, it blows away anything I had before. The lens has minimal Chromatic Aberration and the zoom range is great.
I would definitely recommend this product to others.